This invention generally pertains to gasket assemblies or sealing assemblies. More specifically, the present invention relates to a gasket assembly having an encapsulated locking ring.
The invention is particularly applicable to gasket assemblies suitable for insertion into a groove formed in a bell end of an associated pipe to form a bell and spigot joint. However, it will be appreciated by those skilled in the art that the invention has broader application and may also be adapted for use in many other sealing environments in which one member is inserted in a fluid tight manner into another member.
Pipes are used for the conveyance of water (or other fluids) under pressure, as in penstocks, inverted siphons, and city water lines. They may also be used as free-flow conduits running partly full, as in drains and sewers. Pipes for conveying water in appreciable quantities have been made of steel, cast iron, concrete, vitrified clay, and, most recently, plastic.
It is presently the usual practice to extrude plastic pipes in elongated, cylindrical configurations having a desired diameter and then to cut the extruded product into lengths of a convenient size suitable for handling, shipping and installing. Such sizes may be, for example, ten or twenty foot lengths. Each length of pipe is then enlarged or "belled" at one end sufficiently to join the next adjacent pipe section by receiving in the belled end the unenlarged or "spigot" end of an adjacent length of pipe. The inside diameter of the bell is formed sufficiently large to receive the spigot end of the next section of pipe with sufficient clearance to allow the application of packing, caulking, gaskets or other devices designed to prevent leakage at the pipe joints when a plurality of pipe lengths are joined to form a pipeline. Depending upon the intended pressure of the fluid being conveyed, as well as other design parameters, the seals between adjacent lengths of pipe will be required to be more or less sophisticated.
The pressures a conventional pipeline, and hence the gasket, are exposed to vary from 0 to 250 psi. The American Water Works Association (AWWA) has set the following standards for pipelines: CIPS or high pressure pipe, such as used for fire hydrants and water mains, must withstand 250 psi; IPS or pressurized pipe, such as regular water supply lines, must withstand 160 psi; PIP or plastic irrigation pipe must withstand 50 psi and sewer pipe must withstand 20 psi. As might be expected, gaskets for the CIPS-type pipelines are the most difficult to design. For example, a gasket in a fire hydrant pipeline is under high pressure until the hydrant is opened, at which point the pressure drops precipitously and a vacuum may be formed in the pipeline. The gasket must not only prevent the pressurized water from leaking out at the joints of the pipeline, but must also prevent the entry of air or other infiltrates when a vacuum is pulled on the pipeline.
Prior workers in the art, particularly in the plastic pipe industry, have developed various gaskets which are adapted to be retained within an inwardly facing groove formed in the bell. These gaskets were configured to permit the pipe joint to be quickly made and were intended to be leak proof. While experience has proven that the use of a formed gasket seated within a pipe bell annular groove is an efficient and suitable construction for sealing pipe joints between adjacent lengths of pipes, difficulties have been encountered in maintaining the seal under both high pressure and vacuum conditions. As operating pressures have increased, the difficulties encountered in providing efficient and reliable seals have also increased.
In an effort to solve the sealing problems in high pressure piping systems, prior workers in the art have developed gaskets of the type including extending lips which press against the spigot end. Additionally, other workers have provided gaskets having an inwardly facing peripheral groove within which is seated a locking ring designed to prevent movement of the seal and to discourage gasket blow-out when system pressure or vacuum is applied. Since these locking rings were not centered in the gasket bodies, however, the gaskets were still prone to blow-out.
In a further effort to prevent unseating of the gasket when the pipe joint was made or to prevent blow-out under severe conditions of use, efforts have been made to lock the gasket within the annular groove in the bell. Such efforts by prior workers in the art have included machining the groove to an annular configuration to seat the gasket in the groove. Others have attempted to lock the gasket in the groove by applying, either by a threaded connection or by an adhesive juncture, an outer locking ring or retainer of smaller diameter than the gasket itself. Such prior art attempts to retain the gasket within the groove have, however, not proven to be entirely successful because the end results have not justified the associated increase in gasket complexity and manufacturing costs.
Accordingly, it has been considered desirable to develop a new and improved gasket assembly which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.